This disclosure relates generally to methods and apparatus for generating vibrations or fluid pulses with a downhole tool. More specifically, this disclosure relates to methods and apparatus that enable components of a downhole pulse generating device to be retrieved from the drill string or otherwise facilitate fishing and other through-bore activities.
Downhole pulse generating devices are used to create fluctuations in fluid pressure that create vibrations in the drill string. The vibrations or pulses can help prevent the build-up of solid materials around the drill string, which can reduce friction and prevent the drill string from becoming stuck in the well. Thus, the use of pulse generating devices can be useful in extending the operating range of drilling assemblies.
Conventional pulse generating devices do not allow for fishing or other through bore operations to be performed below the device. Further, pulse generating devices can be difficult to remove from the wellbore without removing substantial portions of the drill string. In many cases, the pulse-generating device must be completely removed from the wellbore to in order to facilitate any fishing or other through-bore activities below the device.
Thus, there is a continuing need in the art for methods and apparatus for facilitating fishing or other through-bore activities below downhole pulse generation devices that overcome these and other limitations of the prior art.